The phase-cut dimming mode has some advantages. It is convenient for users to install and wire the circuit. Further, it is easy to convert the lighting circuit wiring in the old building into a lighting solution with a dimming function. Hence, the phase-cut dimming mode is more and more widely used. However, the current phase-cut dimming power supply generally sacrifices a power factor or efficiency to satisfy the good dimming effect and improve the compatibility with the dimmer. Currently available solution uses a unipolar PFC flyback switching power supply to achieve dimming by adjusting a limited power. Though it can obtain a high power factor, the efficiency is low, which generally provides only 80% conversion effect. Besides, the load range is limited. When the load power is lower than 70% of the rated output power of the power supply, the dimming effect becomes worse. When LED lamps of different colors are connected at the same time, the dimming is unsynchronized. This topological structure determines that the currently available solution is not suitable for the dimming power supply with a power over 100 W, especially not suitable for the phase-cut dimming power supply. Some other solutions realize dimming using a flyback switching power supply or a forward switching power supply without a power factor correction circuit, in a PWM control output mode. Though the efficiency of this mode is a little higher than the efficiency of the phase-cut dimming power supply using the unipolar PFC flyback switching power supply and there is no limit for the load, the power factor is low due to a missing power factor correction circuit. The power factor generally ranges from 0.5-0.8, and the harmonic content is extremely high and is over 100%. Thus, the electric network has high interference. Moreover, the input peak current is high, and the requirement for the rated power or rated current of the dimmer is thus high. Besides, there are some phase-cut dimming power supplies using an electronic transformer. The deficiencies of the phase-cut dimming power supply are that the ripple is extremely large since the output is not filtered, and the voltage regulation and load regulation are both high. Hence, the damage to the LED lamp beads is extremely high when it is used in LED lamps, which reduces the lifetime of the LED lamp beads, and has a significantly obvious stroboscopic issue.
As above, the high power factor phase-cut dimming power supply in the prior art has disadvantages that the load power is limited, dimming is unsynchronized when various LED lamps with different colors are connected, the efficiency is low, and the output power is low and generally lower than 100 W. Furthermore, the phase-cut dimming power supply without a power factor correction has disadvantages of low power factor, high harmonic content, high interference with the electric network, high requirement for the dimmer.
It is to be noted that the phase-cut dimmer has various types, connection configurations and other names, such as a silicon-controlled dimmer, a leading edge dimmer and a trailing edge dimmer, a tangent dimmer or an anti-tangent dimmer. The LED lamp or LED light can also have many forms and types, and can be used individually or in combination.